This invention relates to methods of making shoe soles having outsoles and midsoles.
Conventional dual density shoe soles often have solid rubber outsoles and blown polyurethane midsoles secured to the outsoles. One approach to manufacturing such shoe soles has been to acquire a rubber outsole from a rubber supplier, acquire a blown polyurethane midsole from another source, and bond the midsole to the outsole using a suitable heat-activated adhesive. This manufacturing approach involves utilization of appropriate dry times, heat-activation temperatures (usually 115xc2x0 F. to 140xc2x0 F.) and pressures. Although this process produces suitable shoe soles, it is highly labor intensive and therefore expensive.
A second approach to making a shoe sole with a rubber outsole and polyurethane midsole comprises obtaining a rubber outsole from a rubber supplier, applying a polyurethane adhesive to the upper surface of the outsole, allowing the adhesive to dry, heating the outsole (e.g., 115xc2x0 F. to 140xc2x0 F.) to heat-activate the adhesive, and then pouring a liquid polyurethane directly on the rubber outsole. Although this system can produce suitable shoe soles, it requires the additional time of allowing the adhesive to dry. It also requires the delicate step of heat-activation before pouring of the liquid polyurethane. If the heat-activation step is not performed properly, the midsole might not be adequately bonded to the outsole.
A third approach comprises obtaining a solid rubber outsole which has been specifically formulated and treated with a chlorine solvent solution to accept a liquid polyurethane layer directly from the polyurethane molder without a liquid layer of adhesive being applied. Although this process occasionally produces suitable shoe soles, the results are not consistent enough to guarantee acceptable bonds. Additionally, the treatment on these outsoles degrade with time. Thus, such treated outsoles have a limited shelf life.
Among the several advantages of the present invention may be noted the provision of an improved method of making shoe soles; the provision of such a method which consistently produces high quality shoe soles; the provision of such a method which is not labor intensive; the provision of such a method which produces shoe sole components with a virtually unlimited shelf life; the provision of such a method which minimizes the time necessary to make a shoe sole; the provision of such a method which is cost effective; the provision of an improved outsole component; and the provision of such an outsole component which overcomes the disadvantages associated with the prior art.
In general, a method of the present invention is for making a shoe sole. The method comprises introducing a sheet portion of a thermoplastic material into a first mold, and introducing a quantity of a first sole material into the first mold, using the first mold to form a one piece member comprised of the first sole material and the sheet portion with the sheet portion being secured to the first sole material. The method further comprises introducing the one piece member into a second mold, introducing a quantity of a second sole material into the second mold, the second sole material being in liquid form when introduced in the second mold, and allowing the liquid to cure to a resilient condition such that the cured second sole material is secured to the sheet portion. The second sole material and the one piece member constitute the shoe sole.
Another aspect of the present invention is a method of making an outsole for a shoe sole. The method comprises introducing a sheet portion of a thermoplastic material into a mold, introducing a quantity of an outsole material into the mold, using the mold to form an outsole member comprised of the first sole material and the sheet portion with the sheet portion being secured to the first sole material, and removing the outsole member from the mold.
Another aspect of the present invention is an outsole member for a shoe sole. The outsole member comprises an outsole portion and a thermoplastic urethane layer. The outsole portion is of an elastomeric solid material and includes a bottom surface and a top surface opposite the bottom surface. The bottom surface is adapted for engaging a surface, such as a floor, when a wearer is wearing a shoe comprised of the outsole portion. The thermoplastic urethane layer has a bottom surface and a top surface. The bottom surface of the thermoplastic layer is secured to the top surface of the outsole portion.
Another aspect of the present invention is a shoe sole. The shoe sole comprises an outsole portion of an outsole material, a midsole portion of a midsole material, and a thermoplastic layer between the outsole and the midsole. The thermoplastic layer secures the outsole to the midsole.
Other objects and features will be in part apparent and in part pointed out hereinafter.